Thermostatic switch



Jan. l, 1935. l. w. KNIGHT 1,986,507

THERMOSTATIC SWITCH Filed July 29, 1932 ,2f fm fl *ggf #lie/ww, BY Y M/A TTORNEY. A

Patented Jan. 1, 1935 UNl-TEDSTATES PATENT OFFICE THERMOSTATIC SWITCHIra W. Knight, Providence, R. I., assigner to General Fire ExtinguislierCompany, Providence, B. I., a corporation of Delaware Application July29, 1932, Serial No. 625,778

3 Claims. (Cl. 20o-142) This invention relates to improvements inAFigure 4 is another elevation of tlie same as on thermostatic switches.More especially it relates line 4--4 o! Figure 3;

to improvements in the type of switch disclosed Figure 5 is an elevationlike Figure 3 but with in Letters Patent No. 1,852,312 granted to me onthe parts shown in the positions assumed upon 5 April 5, 1932. operationof the switch; and 5 The switch of the patent is adapted primarilyFigure 6 is an elevation, partly in section, showfor surface mountingwith the binding posts exing an alternative arrangement of the contactternally arranged for connection with exposed Points f0 1 adierent-standby ConditOn.'

wires. Indeed, one of the contact members, (the Befelrlng mOIeparticularly t0 the drawing, the

diaphragm disk) is fully exposed, which is unliglh Shal a'tffekluomeddof 111511195151118' mii;- 10

desirable especially when said member is carryel f 1u: ils f a e I1,h!1OIItlprlSlng a chding live current. And in the patented switch, if itCut'r l? a eb a lfm W Ct Drolc S 9D one .S1 e

becomes necessary to inspect the contact points, :'ocklnlll i);Inangnho't sfr gollf,

rggngisnhn zee rgild :Sutwtle ls housed the contact points 2, 3, one (2)being subl5 stantially immovable and the other (3) being a preventing anoperating test of the points while movable spring point These points areShown thtsiwltch 1s dismantled' as riveted to bushings 4 which fit intosuitabie s an object of the present invention to pro holes in the b tt uf th b d vide a switch for surface mounting with binding th 0, om Wa 0 e0X an are posts internally arranged for connection with readed toreceive binding screws 5. The'latter 20 may bind the terminal ends 6 ofwires directly concealed wires. Indeed it isaieature of the imto thebushings 4 as Shown at the right in proved switch that all theelectricity carrying i members are fully concealed. When inspectiongoglzoor liletnaype Prfvled fpla exteig; of the switch is desired thecontact points are 2 is at on: 5d fetgn) 1S asme b efpf easilyaccessible without disturbing the circuit kinds de engin 0 e gxtn my $1zo 25 connections, thus permitting operative tests to mantainpacirclgngrnwore cled nslrcnmlna mf'ely made while the switch 1s partlydls staiiby or quiescent conditions. If open, the

It is also an object of the invention to provide p0 2 is so dlspoed .asO, overhe the Sprtng not only a spring contact memberwhichfcndguelhnothmeuar; sen1f-lfled mg pomt 30 stantly tends to changeits positionlbut to pro- In either case the movable point Sgiusrield inits vide separate resilient means for normally holdinitial or standbyposition by a button 7 of b mg uns .lmber against s.uch change sald sep'sulated material having an extended point 7a that arate resilient meansbeing so arranged that engages the spring Contact point and having an 35when the swltch as a' whole rsfponds to apre annular shoulder 7b thatrests on the edge of a determined temperature condition the resilienthole 8a in a disk 8 The latter is a simple plain means acts to removeitself and leave the spring nat metallic disk having inherent butnormauy' contact member entirely free to follow its own dormantresiliency. In the arrangement Shown 40 moving force' It is a eature ofme mventlon its edge 8b is clamped between a seat la provided 40 to somount a simple plain fiat metallic disk, havon the base and a ring 9which threads into the ing inherent but dormant resiliency that thisraised Socket rim la This Img has three up resliency is rendered activeby the mere fast standing arms 9a which come together above the enmg ofme fnsk button and form a supporting yoke for a ther- While itisintended that the patent shall cover many responsive element 10 that isinte d 45 by suitable expression in the appended claims between the yokeand the button Ip use whatever features of patentable novelty exists Theelement disclosed here is a Sealed frangiin the invention disclosed, apreferred embOdble vessel having 9, charge of fluid which upon l ment isshown in the accompanying drawing, in being heated to a predeterminedtemperature is which: adapted to completely shatter the vessel. The 50Figure 1 is a plan of the improved Switch; latter is preferably of thebulb type with a some- Figure 2isan elevation; what attenuated neck 10aat one end that fits Figure 3is an elevation in sectionas on line 3-3into a suitable hole '1c in the button and with of Figure 2 showing theswitch in one standby a top or upper end that rests against a thimblecondition; seat il secreted in head of are yoke. The dis- 55 tancebetween the top of the yoke and the point 'la of the button is such thatwhen the yoke ring 9 is screwed into the socket rim 1c and firmly clampsthe edge 8b of the disk to the base, the spring contact point 3 will beeither separated from the point 2 as in Figure 3 or pressed into contactwith it (2') as seen in Figure 6. In either case the spring point isbent against its own resilient resistance so that it stands ready toabruptly change its relation to the other point whenever the control ofthe button is removed.

This, as before indicated, takes place upon the giving way of thethermally' responsive element 10 which in the case of the chargedfrangible vessel illustrated means a complete annihila tion of theelement. As this occurs the button 7 is snapped free of the springcontact point 3 by the action of the disk 8, leaving the full resilientforce of the spring point 3 available to change its relation with theother point.

'I'his active force of the disk is insured by the novel manner in whichits edge 8b is clamped so as to be held at an angle to the normal planeof the disk. That is, the edge is so held that the disk is dished upwardwith its concave side toward the contact points. The disk may be securedto either the base or the yoke member by suitable retaining means or, asherein disclosed, may be clamped between the yoke member and the base.The ring-shaped surface 1d of the latter, upon which the disk edgerests, is formed at a slight angle to the plane of the base with theinner edge of the surface being most removed from said plane and withthe remainder of the surface approaching nearer to the said plane. Thebottom edge 9b of the yoke ring is correspondingly disposed so that theface which engages the disk is parallel to the angularly disposedannular seat 1d of the base. In consequence, when the yoke is screwedinto the raised socket rim 1c and comes to bear upon the disk, the edgeof the latter is bent downward as c1ear` ly seen in Figures 3, 4 and 5.If there were no vessel or button interposed between the yoke arms andthe disk, the latter would assume the position shown in Figure 5, infact this is the position of the disc when the vessel has beendestroyed. But in assembling the switch the vessel and button will beinterposed between the yoke and disk so that as the yoke ring turns intothe socket rim and firmly clamps the disk edge to the angular seat onthe base the disk will be bowed or dished inward as seen in Figures 3and 4. Since it would otherwise be dished outward, as already explained,it is clear that when dished inward there is established in the disk aresilient force tending strongly to snap the disk to the position shownin Figure 5.' Thus it is that when the vessel is destroyed the disksnaps outward due to the said resilient force and pushes the button 7clear of the spring contact point 3 (indeed the button is usually thrownclear of the switch) leaving the latter free to move with respect to theother contact point.

The provision of force for moving the disk and button is of realadvantage because it is not uncommon to nd switches, especially wheninstalled With the yoke upward as herein shown, considerably loaded.That is, dust and other foreign matter collects on the disk and buttonand, in cases where a switch enjoys a prolonged period of idleness, thiscollection may have an appreciable weight. If this weight of foreignmatter as well as that of the button and disk were to be moved solely bythe force of the spring contact point, it is clear that the action ofthe latter would be at least impeded if not indeed prevented. In theswitch of the invention the contact points are completely housed and sono loaded condition of the spring point can occur, and because of theresilient force imposed upon the disk by its manner of mounting theloading of the latter can be disregarded since the force thus imposedwill insure the prompt movement of the disk and button and the immediaterelease 0f the spring point with all its own force available to causeits change in relation with the other Apoint.

Although the switch is shown and has been described as positioned withthe yoke uppermost, it is to be understood that the switch can beinstalled in any position. Since all the current carrying parts areassociated with the box, if the latter is placed in a recess with thecircular plate 1a attached to the surface of the material surroundingthe recess the said parts and the wires leading thereto may be entirelyconcealed. If it is desired to test the connections and determine theoperativeness of the contact points the yoke can simply be unscrewedfrom the base,

and the vessel, button and disk lifted out. This will completely exposethe contact points and they can be manually actuated to test thecircuit.

To restore the switch to normal standby condition the removed parts needonly be returned to their initial positions. If no testing of the switchis anticipated, the yoke may be sealed in the base to prevent itsremoval by an unauthorized individual.

'I'he three-armed yoke serves as a protector of the frangible vesselfromaccidental blows of passing objects, yet provides ample space for thefragments of the vessel to ny clear when its (shattering occurs. Theprovision of the box on one side of the base plate, so that it may beplaced in a recess, makes the switch as a whole stand close to thesurface towhich it is attached, making it less conspicuous, less` apt toexcite the curiosity of an inquisitive observer, and less likely to beaccidentally hit.

I claim:

1. A thermostatic switch comprising a base having an enclosed chamber onone side thereof; a substantially immovable contact point and a movablespring contact point arranged in said chamber; a disk mounted inposition to form a yieldable cover for said chamber; a support attachedto said base and outstanding therefrom on the side thereof opposite tosaid chamber; means interposed between said support and said diskcomprising a charged frangible vessel adapted upon being heated to apredetermined temperature to destroy itself and a seating member forsaid bulb engaging the edge of a hole in the disk and extendingtherethrough into engagement with thespring contact point, whereby thesaid point is normally held in predetermined relation to the otherpoint; the last said means of saidY disk havinga surface disposed at anangle to the normal plane of the disk whereby the disk being clamped tosaid seat it tends to dish outward with respect to the contact points;and means interposed between the member and said disk and engaging acontact point whereby the said disk is'normally held dished inwardtoward the contact points and the engaged point is held in predeterminedrelation to another point; the last said means remaining undisturbed asrespects the said holdings until a predetermined temperature is reachedand then giving way to permit said disk to snap outward and separatesaid means from said engaged contact point thereby permitting the saidpoints to alter their relation to one another.

3. A thermostatic switch comprising a base having a chamber therein andan internally threaded rim; a seating surface within said rim disposedat an angle to the plane of said base; a resilient disk arranged withits outer edge overlying said seating surface and having a centralopening; an open frame member having a base portion fitting saidinternally threaded rim and provided with a seating surface parallel tothe said seating surface o1' the base, whereby upon the member beingscrewed into the rim the edge of the disk is clamped between saidseating surfaces and the disk is caused to flex outward from thechamber; contact members in the said chamber capable of assuming apredetermined relation with one another; a button seated on the edge ofthe central opening of said disk having a portion extendingtherethrough; and heat actuated means interposed between said button andsaid frame member for holding said button against the resilient force ofthe disk' against one of the contact members to thereby alter theirpredetermined relation; the last means giving way when a predeterminedtemperature is reached to permit the disk to remove the button fromcontact with the contact member and thereby enable said contact membersto assume their predetermined relation.

IRA W. KNIGHT.

